The invention relates to a write head and to an apparatus.
In modern tape systems, data is organized in data tracks which are written and read back in a parallel fashion by a head assembly comprising data read and write heads, i.e., transducer elements. These data tracks run in the longitudinal direction of the magnetic tape and are much narrower than the excursions the magnetic tape experiences in the lateral direction as a result of imperfections in the mechanical entrainment system. Therefore, it is crucial to accurately position the head assembly relative to the magnetic tape in the lateral direction, and to maintain this relative position as the magnetic tape is streamed. To this end, as well as for other purposes, media manufacturers write servo tracks on the magnetic tape parallel to and interleaved with the data tracks. Servo read heads on the head assembly read the servo information stored in the servo tracks, which is then used for aligning the data read and write heads with the data tracks on the magnetic tape.
Servo tracks are typically written to the magnetic tape using one servo write head for each servo track. Each servo write head generally comprises a yoke having one or more gaps and a coil for producing a magnetic field at each gap. The write heads, in particular the gaps, are configured to imprint a specific pattern on the magnetic tape via fringing magnetic fields. This pattern, generally based on chevron shapes, contains the information required to determine the instantaneous lateral location of the data read and write heads (or the head assembly as a whole) using a time-based-servo (TBS) scheme as for example described in EP 0 690 442 A2.
For a TBS servo scheme to work accurately, one requirement is that several portions of the pattern located at different positions along the direction of motion of magnetic tape (e.g. the two branches of a chevron pattern) are written simultaneously, so that their imprints in the magnetic tape are always located at a fixed and accurate distance from each other independently of velocity jitter.